Benzoheterocyclic anti-bacterial agents

ABSTRACT

Embodiments herein provide compounds and methods of making and using such compounds for prevention and treatment of multidrug resistant bacteria. In particular, embodiments are directed to anti-bacterial agents from benzo[d]heterocyclic scaffolds for prevention and treatment of multidrug resistant bacteria.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.12/995,437, filed Nov. 30, 2010, which is a continuation ofInternational Application No. PCT/US2009/045737, filed May 29, 2009,which claims priority to U.S. Provisional Patent Application No.61/057,282, filed May 30, 2008, the entire disclosures of which arehereby incorporated by reference in their entirety.

GOVERNMENT INTERESTS

This invention was made with government support under Grant No. R01 AI054193 awarded by the National Institutes of Health. The United StatesGovernment has certain rights in the invention.

TECHNICAL FIELD

Embodiments herein relate to anti-bacterial agents, and, morespecifically, to anti-bacterial agents from benzo[d]heterocyclicscaffolds for prevention and treatment of multidrug resistant bacteria.

BACKGROUND

In 2004, the IDSA (Infectious Disease Society of America) reported thateach year 90,000 of the 2 million people who acquire a hospitalbacterial infection will die. That is a 4.5% mortality rate arising fromjust being within the hospital. Multi-drug resistance bacterial strainsare a major problem and one that has been increasing very rapidly everyyear during the last few decades. In brief, from its discovery in 1968multi-drug resistant Staphylococcus aureus (MRSA) had already accountedfor greater than 50% of S. aureus patient isolates by 1999 in ICUs(intensive care units) within the National Nosocomial InfectionSurveillance (NNIS) System. Then by 2003, 59.5% of isolates were fromMRSA. Vancomycin resistant enterocci (VRE) has had a similar rapid risein hospital isolates increasing from its 1990 discovery to 25% of allenterococal isolates in 1999 and then increasing further to 28.3% by2003 in NNIS surveyed ICUs. Without the immediate discovery of newantibiotics, this rise in multi-drug resistant strains will continue togrow thereby putting everyone treated within hospitals at undue risk ofinfection and possible death.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments will be readily understood by the following detaileddescription in conjunction with the accompanying drawings. Embodimentsare illustrated by way of example and not by way of limitation in thefigures of the accompanying drawings.

FIG. 1 illustrates a general scheme for the synthesis of variousbenzo[d]heterocyclic compounds for the treatment of multidrug resistantbacteria in accordance with various embodiments.

FIG. 2 is a flowchart of initial analogs generated to explore theeffects on antibacterial potency and selectivity of nitrofuranreplacement with nitrothiophene in accordance with embodiments herein.

FIG. 3 illustrates specific examples of the syntheses used to makebenzimidazoles from aldehydes, benzthiazoles from nitriles, andbenzoxazoles from acid chlorides in accordance with embodiments.

FIG. 4 illustrates selectivity and potency of various benzimidazoles,benzthiazoles, and benzoxazoles against a panel of microorganismsincluding gram-positive bacteria, gram-negative bacteria, fungi, yeast,and mycobacteria.

FIG. 5 illustrate the chemical structure, molecular weight, and chemicalformula of most of the compounds of FIG. 4.

FIG. 6 illustrates the potency of various benzo[d]heterocyclic compoundsagainst methicillin-resistant Staphylococcus aureus (MRSA) in micromolarconcentration.

FIG. 7 illustrates the potency of various imidazopyridine compoundsagainst MRSA in micromolar concentration.

FIG. 8 illustrates the potency and selectivity of an exemplary compoundagainst a panel of MRSA clinical isolates compared to a Vancomycinstandard in micrograms per milliliter.

FIG. 9 illustrates the potency and selectivity of an exemplary compoundagainst a panel of Gram-positive clinical isolate strains compared to aCiprofloxacin standard in micrograms per milliliter.

FIG. 10 illustrates the potency and selectivity of an exemplary compoundagainst a panel of Gram-negative clinical isolate strains compared to aCiprofloxacin standard in micrograms per milliliter.

FIG. 11 illustrates the minimum inhibitory concentration (MIC) and theminimum bactericidal concentration (MBC) determinations of an exemplarycompound to various Gram-positive strains.

FIG. 12 illustrates results of a time-kill assay of an exemplarycompound against a methicillin-sensitive S. aureus strain (MSSA).

FIG. 13 illustrates a mutational analysis of an exemplary compound bygrowth of S. aureus strains.

FIG. 14 illustrates the mutational analysis of an exemplary compound byserial transfer experiments.

DETAILED DESCRIPTION

In the following detailed description, reference is made to theaccompanying drawings which form a part hereof, and in which are shownby way of illustration embodiments that may be practiced. It is to beunderstood that other embodiments may be utilized and structural orlogical changes may be made without departing from the scope. Therefore,the following detailed description is not to be taken in a limitingsense, and the scope of embodiments is defined by the appended claimsand their equivalents.

Various operations may be described as multiple discrete operations inturn, in a manner that may be helpful in understanding embodiments;however, the order of description should not be construed to imply thatthese operations are order dependent.

For the purposes of the description, a phrase in the form “A/B” or inthe form “A and/or B” means (A), (B), or (A and B). For the purposes ofthe description, a phrase in the form “at least one of A, B, and C”means (A), (B), (C), (A and B), (A and C), (B and C), or (A, B and C).For the purposes of the description, a phrase in the form “(A)B” means(B) or (AB) that is, A is an optional element.

The description may use the terms “embodiment” or “embodiments,” whichmay each refer to one or more of the same or different embodiments.Furthermore, the terms “comprising,” “including,” “having,” and thelike, as used with respect to embodiments, are synonymous.

Embodiments herein provide compounds and methods of making and usingsuch compounds for prevention and treatment of multidrug resistantbacteria.

In embodiments, the aryl or heteroaryl[d]heterocyclic derived compoundsshow impressive activity against multidrug resistant strains of bacteriaincluding Methicillin-resistant Staphylococcus aureus (Methicillin-RSA),Vancomycin-Resistant Enterococcus (VRE), and Linezolid-ResistantEnterococcus (LRE) infections with potencies near or beyond that ofcurrent clinical treatments. In embodiments, these compounds are alsoeffective against Bacillus subtilis, Escherichia coli, Pseudmonadasaeruginosa, Mycobacterium vaccae, Sporobolomyces salmonicolor, Candidaalbicans, Penicilluum notatum and Mycobacterium tuberculosis to variousextents. Thus, in embodiments, methods of using one or more compoundsdescribed herein may be provided for the prevention and/or treatment ofmultidrug resistant bacteria.

In accordance with an embodiment, exemplary compounds may be prepared bythe scheme in FIG. 1, which illustrates a general scheme for thesynthesis of various benzo[d]heterocyclic compounds for the treatment ofmultidrug resistant bacteria.

In FIG. 1, reagents include: a) Oxalyl chloride, CH₂Cl₂, catalyticN,N-dimethylforamide; b) N-(3-dimethylaminopropyl)-N-ethylcarbodiimidehydrochloride, Et₃N, CH₃CN; c) Et₃N, CH₂Cl₂, reflux; d) Acetic acid,reflux; e) (Diethylamino)sulfur trifluoride, K₂CO₃, CH₂Cl_(2, −78)° C.to room temp.; and f) p-toluenesulfonic acid, toluene, reflux.

In an embodiment, these compounds may be prepared by an EDC-mediatedcoupling of 1 or displacement of an acid chloride 2 with 3, base andproper solvent to give an amide 4. Cyclization of the amide 4 with oneof the above conditions (depending on Y substituent) results inheterocyclic products 5.

In FIG. 1, compound 3, Y is H, O, SH, SR₁, NH₂, NHR₁, CH₂NH₂, CH₂SH,CH₂OH, CH₂NHR₁, CH₂SR₁. In FIG. 1, compound 5 may comprise thefollowing: R₁ is H, alkyl, substituted alkyl, including halogenatedalkyl such as CF₃, aryl and substituted aryl, halogen, cycloheteroalkyl(such as morpholine, thiomorpholine, piperazine, piperidine), aryl,heteroaryl, substituted heteroaryl, nitro, sulfone, sulfoxide,sulfamide, phosphate, alkylphosphate (such as PO(CH₃)₂, PO(OCH₃)₂)boronic acid, or boronic ester; X is O, S, N, or CH₂; n=0-8, saturatedor unsaturated; Y is O, S, N, or CH₂; m=0-3; R₂ is H, OH, halogen,amine, COOH, NHR₁ (wherein R₁ is as previously defined), NR₁R₁, alkyl,substituted alkyl, cycloalkyl, or functionalized alkyl (includingalkenes, alkynes, alcohols, epoxides, ketones, esters, ethers,aldehydes, nitriles, nitros, thiols, thioesters, sulfides, disulfide,sulfones, sulfoxides, amines, amides, ureas, carbamates),cycloheteroalkyl (such as morpholine, thiomorpholine, piperazine,piperidine), acyl, halogenated acyl, substituted acyl, aryl, substitutedaryl, heteroaryl, substituted heteroaryl, heterocylic (such as furan,nitrofuran, thiophene, nitrothiophene, imidazole, oxazole, oxazoline,thiazole, thiazoline, triazole, pyridine, pyrazine, naphthalene,diketopiperazine, quinoline, isoquinoline, imidazopyridines,oxazolidinone, and all substitutions upon), wherein R₂ may bemonosubstituted or polysubstituted; and Z is N in the 2, 3, 4, or5-positions of the phenyl ring and any combination therein (with the2-position being exemplified by the structure shown).

In embodiments, compounds may be formed as a prodrug to enhance thedelivery of the compound, such as enhancing absorption, distribution,metabolism, excretion, etc. Suitable groups to provide a prodrug may,for example, entail modifying an OH group to form an O-prodrug group,wherein the prodrug group is one of acyl, ester, carbamate, urea, sugar,or amino acid.

In embodiments, various molecules as described herein have surprisingactivity against MRSA. One exemplary compound tested (nitrofuranbenzimidazole), showed results against MRSA of (MIC=8 μM) and againstVRE (MIC=16 μM). While this particular molecule has been testedpreviously, the present application is the first disclosure of thiscompound having activity against multi-drug resistant “super bug”strains. In addition, in accordance with an embodiment described herein,this compound and analogs thereof may be synthesized in high yields injust a single step. Further embodiments herein provide analogs of theafore-mentioned compounds and methods of making and using suchcompounds.

In a time of rapid and increasing resistance toward the last lineantibacterial agents like Vancomycin and Linezolid, it is prudent thatinvestigation of all new leads undertaken. In an embodiment, a set ofanalogs (see FIG. 2) were produced in order to explore potency andantimicrobial selectivity. The next generation of benzoxazole andbenzthiazole derivatives, as well as the effects of substitution of thebenzimidazole core on antibacterial potency and selectivity, wereexplored.

Synthesis of analogs was accomplished in a simple straightforward manneras shown in FIG. 3. FIG. 3 illustrates specific examples of thesyntheses used to make benzimidazoles from aldehydes, benzthiazoles fromnitriles, and benzoxazoles from acid chlorides. Fortuitously, manycompounds may be made in a just one step. For instance, condensation of5-nitro-2-furaldehyde 1 (where X is O) or 5-nitro-2-thiophenealdehyde 1(where X is S) with various diamines, 2, followed by oxidation withpotassium ferricyanide results in a panel of substituted benzimidazoles,3a to 3g. Next, the benzthiazoles (6a and 6b) may be easily prepared byan acid catalyzed cyclization of nitrile, 4, and 2-aminothiophenol (5).Finally, benzoxazoles (11a and 11b) may be prepared in a two stepprocess involving coupling of easily prepared acid chloride, 8, with2-aminophenol (9) to give intermediate amide (10) which may then becyclized with p-toluenesulfonic acid in refluxing toluene.

In FIG. 3, the reagents include: (a) KFe(CN)₆, CH₃OH, water, reflux, 2h-16 h; (b) p-TSOH, ethanol, reflux, 16 h; (c) Oxalyl chloride, CH₂Cl₂,DMF (drop), 4 h; (d) Et₃N, CH₂Cl₂, reflux, 16 h; and (e) p-TSOH,toluene, reflux, 16 h.

In accordance with an embodiment, in order to first broadly screen thesecompounds, an agar diffusion assay was employed to determine whetherthese compounds have any activity against a diverse array of organismswhich include MRSA and VRE. Then to follow up, if a compound showedpromise (by having a large zone of inhibition) its minimum inhibitionconcentration at 90% (MIC) would be determined for that specificorganism (FIG. 4). FIG. 4 illustrates selectivity and potency of variousbenzimidazoles, benzthiazoles, and benzoxazoles against a panel ofmicroorganisms including gram-positive bacteria, gram-negative bacteria,fungi, yeast, and mycobacteria. The minimum inhibition concentration at90% is shown in micromolar concentration. In an embodiment, the initialagar diffusion assay screen was encouraging as it hinted that many ofthese compounds have a broad spectrum of activity while others showedsome specificity towards specific organisms. Therefore many of thecompounds had their MICs determined which reflected many of the findingsof the diffusion assay. FIG. 5 illustrates the chemical structure,molecular weight, and chemical formula of most of the compounds of FIG.4.

FIG. 6 illustrates the potency of various benzo[d]heterocyclic compoundsagainst methicillin-resistant Staphylococcus aureus (MRSA) in micromolarconcentration. FIG. 7 illustrates the potency of various imidazopyridinecompounds against MRSA in micromolar concentration.

All the anhydrous solvents, reagent grade solvents for chromatographyand starting materials were purchased from either Aldrich Chemical Co.(Milwaukee, Wis.) or Fisher Scientific (Suwanee, Ga.). General methodsof purification of compounds involved the use of silica cartridgespurchased from AnaLogix, Inc. (Burlington, Wis.; www.ana-logix.com)and/or recrystallization. The reactions were monitored by thin-layerchromatography (TLC) on precoated Merck 60 F₂₅₄ silica gel plates andvisualized using UV light (254 nm).

All compounds were analyzed for purity and characterized by ¹H and ¹³CNMR using a Varian 300 MHz NMR and Varian 500 MHz NMR spectrometer.Chemical shifts are reported in ppm (δ) relative to the residual solventpeak and coupling constants (J) are reported in hertz (Hz) (s=singlet,bs=broad singlet, d=doublet, dd=double doublet, bd=broad doublet,ddd=double doublet of dublet, t=triplet, tt=triple triplet, q=quartet,and m=multiplet) and analyzed using MestReC NMR data processing.

Mass Spectra values are reported as m/z. All reactions were conductedunder Argon unless otherwise noted. Solvents were removed in vacuo on arotary evaporator. The LC/MS analyses were carried out on Waters ZQinstrument consisting of chromatography module Alliance HT, photodiodearray detector 2996, and mass spectrometer Micromass ZQ, using a 3×50 mmPro C18 YMC reverse phase column. Mobile phases: 10 mM ammonium acetatein HPLC grade water (A) and HPLC grade acetonitrile (B). A gradient wasformed from 5% to 80% of B in 10 minutes at 0.7 mL/min. The MSelectrospray source operated at capillary voltage 3.5 kV and adesolvation temperature 300° C. Elemental analyses were performed byMidwest Microlabs, LLC (Indianapolis, Ind.). Yields quoted areunoptimized.

Abbreviations: DCM=dichloromethane; DMF=dimethylformamide;ACN=acetonitrile; EtOAc=ethyl acetate; HOAc=acetic acid;EDCI═N-(3-Dimethylaminopropyl)-N¹-ethylcarbodiimide hydrochloride;DMAP=4-dimethylaminopyridine; Et₃N=triethylamine; and EtOH=ethanol.

The synthesis and testing of an exemplary compound (ND-7901) aredetailed below.

5-Nitro-2-furaldehyde (1a, 401 mg, 2.8 mmol) and 2,3-diaminophenol (2 g,300 mg, 2.4 mmol) were dissolved in 10 mL of methanol. Next, a 5 mLaqueous solution of potassium ferricyanide (1.7 g, 5.1 mmol) was addedand the reaction was heated to reflux for 16 hours while being exposedto air. Then the reaction was cooled, filtered and the filter pad waswashed with ethanol. The filtrate liquor and washings were combined andconcentrated in vacuo and the residue was recrystallized from EtOH:H₂O(80/20 to give 180 mg of 3g as a dark solid (26%) after filtration. ¹HNMR (300 MHz, DMSO) δ 7.90 (1 H, m), 7.42 (1 H, m), 7.06 (2 H, m), 6.59(1 H, m); HRMS calcd. for C₁₁H₇N₃O₄, 246.0515 found 246.0504. LC/MSRetention time 4.73 min (>95%), FABMS 246.4 (M+1).

FIG. 8 illustrates the potency and selectivity of ND-7901 against apanel of MRSA clinical isolates compared to a Vancomycin standard inmicrograms per milliliter.

FIG. 9 illustrates the potency and selectivity of ND-7901 against apanel of Gram-positive clinical isolate strains compared to aCiprofloxacin standard in micrograms per milliliter. ND-7901 exhibitsgood activity against Gram-positive isolates. FIG. 10 illustrates thepotency and selectivity of ND-7901 against a panel of Gram-negativeclinical isolate strains compared to a Ciprofloxacin standard inmicrograms per milliliter. ND-7901 has limited activity againstGram-negative isolates.

FIG. 11 illustrates the minimum inhibitory concentration (MIC) and theminimum bactericidal concentration (MBC) determinations of ND-7901 tovarious Gram-positive strains. A series of broths were mixed withsolutions of diluted drug an inoculum was applied. After incubation, theMIC was determined as the first concentration in which the growth of theorganism has been inhibited. In contrast, the MBC was measured byinoculating the series of broths used for the MIC determination ontodrug-free medium. The MBC is the first dilution at which growth is notobserved. ND-7901 is bactericidal against most Gram-positive isolates.

FIG. 12 illustrates results of a time-kill assay of ND-7901 againstmethicillin-sensitive S. aureus (MSSA), ATCC 29213, showing the rapidkinetics of bacteria death when treated with drug at variousconcentrations with Vancomycin as the control.

FIG. 13 illustrates a mutational analysis of ND-701 by growth of S.aureus strains overnight with no selection and recovery of resistantcolonies on drug plates at 2-4 times the MIC value. ND-7901 shows verylow mutation such that no spontaneous mutants were recovered.

FIG. 14 illustrates the mutational analysis of ND-7901 by serialtransfer experiments. As such, the S. aureus strains were grown withND-7901 (0.5-2 times the MIC) added and passed serially until resistancewas found. ND-7901 shows a very low level of resistance after 8passages.

The synthesis and testing of various related compounds are detailedbelow.

5-Nitro-2-furaldehyde (1a, 1.0 g, 7.0 mmol) and 1,2-phenylenediamine(2a, 658 mg, 6.0 mmol) were dissolved in 15 mL of methanol. Next, an 8mL aqueous solution of potassium ferricyanide (4.2 g, 12.6 mmol) wasadded and the reaction was heated to reflux for 3 hours while exposed toair. The reaction was cooled, then filtered and the filter pad waswashed with ethanol. The filtrate liquor and washings were combined,concentrated in vacuo and the residue was recrystallized with EtOH:H₂O(80/20) to give 1.34 g of 3a as a red-tan solid (83%) after filtration.Mp 225-226° C.; ¹H NMR (300 MHz, DMSO) δ 7.91 (1 H, d, J=3.9 Hz), 7.66(2 H, m), 7.48 (1 H, d, J=3.7 Hz), 7.30 (2 H, m); HRMS calcd. ForC₁₁H₇N₃O₃, 230.0566 found 230.0561. LC/MS Retention time 5.55 min(>95%), FABMS 230.3 (M+1).

5-Nitro-2-thiophenecarboxyaldehyde (1b, 500 mg, 3.1 mmol) and1,2-phenylendiamine (2a, 286 mg, 2.6 mmol) were dissolved in 10 mL ofmethanol. Next, a 5 mL aqueous solution of 1.57 grams of potassiumferricyanide was added and the mixture was heated to reflux for twohours. Then the reaction was cooled, filtered and filter pad was washedwith ethanol. The filtrate liquor and washings were combined andconcentrated in vacuo and the residue was recrystallized from EtOH:H₂O(80/20). A dark tan solid of 3b was collected by filtration, 180 mg(28%). ¹H NMR (300 MHz, DMSO) δ 8.24 (1 H, d, J=4.4 Hz), 7.84 (1 H, d,J=4.4 Hz), 7.65 (2 H, m), 7.29 (2 H, m); HRMS calcd. for C₁₁H₇N₃O₂S,246.0337 found 246.0324. LC/MS Retention time 6.53 min (<95%), FABMS244.4 (M−1).

5-Nitro-2-furaldehyde (1a, 304 mg, 2.1 mmol) and4-chloro-1,2-phenylyenediamine (2c, 253 mg, 1.8 mmol) were dissolved in10 mL of methanol. Next, a 10 mL aqueous solution of potassiumferricyanide (821 mg, 3.2 mmol) was added and the reaction was heated toreflux for 16 hours with exposure to air. The reaction was cooled, thenfiltered and the filter pad was washed with ethanol. The filtrate liquorand washings were combined and concentrated in vacuo and the residue wasrecrystallized from EtOH:H₂O (80/20) to give 257 mg of 3c as a darkgreen solid (55%) after filtration. Mp 230-235° C.; ¹H NMR (300 MHz,DMSO) δ 7.96-7.82 (1 H, bs), 7.76-7.57 (2 H, bs), 7.55-7.43 (1 H, bs),7.37-7.23 (1 H, bs); HRMS calcd. for C₁₁H₆ClN₃O₃, 264.0176 found264.0189. LC/MS Retention time 7.03 min (>95%), FABMS 264.2 (M+1).

5-Nitro-2-furaldehyde (1a, 310 mg, 2.2 mmol) and4-fluoro-1,2-phenylyenediamine (2d, 230 mg, 1.8 mmol) were dissolved in10 mL of methanol. Next, a 10 mL aqueous solution of potassiumferricyanide (837 mg, 3.2 mmol) was added and the reaction was heated toreflux for 3 hours with exposure to air. Then the reaction was cooled,filtered and the filter pad was washed with ethanol. The filtrate liquorand washings were combined and concentrated in vacuo and the residue wasrecrystallized from EtOH:H₂O (80/20) to give 111 mg of 3d as ayellow-green solid (25%) after filtration. Mp 235-240° C.; ¹H NMR (300MHz, DMSO) δ 7.96-7.84 (1 H, bs), 7.75-7.60 (1 H, bs), 7.58-7.38 (2 H,bs), 7.27-7.08 (1 H, bs); HRMS calcd. for C₁₁H₆FN₃O₃, 248.0471 found248.0474 found. LC/MS Retention time 6.07 min (>95%), FABMS 248.3 (M+1).

5-Nitro-2-furaldehyde (1a, 306 mg, 2.1 mmol) and 2,3-diaminobenzoic acid(2e, 281 mg, 1.8 mmol) were dissolved in 10 mL of methanol. Next, a 5 mLaqueous solution of potassium ferricyanide (1.3 g, 3.8 mmol) was addedand the reaction was heated to reflux for 16 hours while exposed to air.Then the reaction was cooled, filtered and the filter pad was washedwith ethanol. The filtrate liquor and washings were combined andconcentrated in vacuo and the residue was recrystallized from EtOH:H₂O(80/20) to give 512 mg of 3e as a brown solid (88%) after filtration. ¹HNMR (300 MHz, DMSO) δ 8.22 (1 H, s), 7.88 (1 H, d, J=3.9 Hz), 7.82 (1 H,d, J=8.2 Hz), 7.63 (1 H, d, J=3.9 Hz), 7.56 (1 H, d, J=8.5 Hz); HRMScalcd. for C₁₂H₇N₃O₅, 274.0464 found 274.0446. LC/MS Retention time 3.05min (>95%), FABMS 274.3 (M+1).

5-Nitro-2-furaldehyde (1a, 407 mg, 2.8 mmol) and 2,3-diaminotoluene (2f,300 mg, 2.4 mmol) were dissolved in 10 mL of methanol. Next, a 5 mLaqueous solution of potassium ferricyanide (1.7 g, 5.1 mmol) was addedand the reaction was heated to reflux for 3 hours while exposed to air.The reaction was cooled, then filtered and the filter pad was washedwith ethanol. The filtrate liquor and washings were combined andconcentrated in vacuo and the residue was recrystallized from EtOH:H₂O(80/20) to give 519 mg of 3f as a brown solid (75%) after filtration. ¹HNMR (300 MHz, DMSO) δ 7.82 (1 H, d, J=3.9 Hz), 7.40 (2 H, m), 7.11 (1 H,t, J=7.6, 7.6 Hz), 7.01 (1 H, d, J=6.8 Hz); HRMS calcd. for C₁₂H₉N₃O₃,244.0722 found 244.0729. LC/MS Retention time 6.32 min (>95%), FABMS244.4 (M+1).

5-Nitro-2-furonitrile (4a, 185 mg, 1.3 mmol) was dissolved in 10 mL ofethanol and then the 2-aminothiophenol (5, 0.15 mL, 1.4 mmol) andp-toluenesulfonic acid, monohydrate (240 mg, 1.3 mmol) were added andthe reaction was heated to 80° C. overnight. The reaction wasconcentrated to dryness in vacuo and then the residue was dissolved inEtOAc and washed with 10% sodium bicarbonate (2×), 0.5 N citric acid(2×) and then satd. brine solution. The organic phase was collected anddried over sodium sulfate, filtered and then concentrated in vacuo togive a dark oil. The material was purified through a silica gel columneluting with 100% DCM and product 6a was collected as a yellow-tansolid, 75 mg (24%). ¹H NMR (300 MHz, DMSO) δ 8.31-8.12 (1H, m), 7.82 (1H, dd, J=66.5, 4.0 Hz), 7.69-7.53 (1 H, m), 7.48 (1 H, d, J=8.0 Hz),7.14-7.08 (2 H, m); HRMS calcd. for C₁₁H₆N₂O₃S, 247.0177, found247.0171. LC/MS Retention time 8.07 min (<95%), FABMS 247.2 (M+1).

5-Nitro-2-thiophenecarbonitrile (4b, 206 mg, 1.3 mmol) was dissolved in10 mL of ethanol and then the 2-aminothiophenol (5, 0.15 mL, 1.4 mmol)and p-toluenesulfonic acid, monohydrate (243 mg, 1.3 mmol) were addedand the reaction was heated to 80° C. overnight. The reaction wasconcentrated to dryness in vacuo and the residue was dissolved in EtOAcand washed with 10% sodium bicarbonate (2×), 0.5 N citric acid (2×) andthen satd. brine solution. The organic phase was collected, dried oversodium sulfate, filtered and then concentrated in vacuo to give a redoil. The residual material was triturated with dichloromethane and 6bwas obtained as red solid after filtration, 125 mg (37%). ¹H NMR (300MHz, DMSO) δ 8.22 (1 H, dd, J=2.3, 0.8 Hz), 8.20 (1 H, s), 8.14-8.08 (1H, m), 7.95 (1 H, dd, J=4.4, 0.8 Hz), 7.64-7.50 (2 H, m); HRMS calcd.for C₁₁H₆N₂O₂S₂, 263.9949, found 263.9953. LC/MS Retention time 9.55 min(<95%), FABMS 263.3 (M+1).

5-Nitro-2-furoic acid (7a, 1.5 g, 9.4 mmol) was partly dissolved in 20mL of dry dichloromethane. Oxayl chloride (1.8 mL, 21.3 mmol) was addedfollowed by a few drops of DMF. The reaction was stirred for 4 hoursthen concentrated to dryness in vacuo to give intermediate acidchloride, 8a, as yellow oil which became solid upon standing, 1.0 g(99%). 5-Nitrofuran-2-carbonyl chloride (8a, 624 mg, 3.5 mmol) wasdissolved in 10 mL of anhydrous dichloromethane and the solution wascooled to 0° C. 2-Aminophenol (9, 460 mg, 4.2 mmol) was added followedby Et₃N (1.4 mL, 10.5 mmol) and the reaction was then allowed to warm toroom temperature and stirred overnight. The reaction was concentrated todryness in vacuo then diluted with EtOAc (75 mL) and washed with 0.5 Ncitric acid (2×), 10% sodium bicarbonate soln. (2×) and then satd.brine. The organic phase was dried over sodium sulfate and concentratedin vacuo to give a yellow film. The residual material was trituratedwith dichloromethane and upon cooling a yellow solid ofN-(2-hydroxyphenyl)-5-nitrofuran-2-carboxamide, 10a, was collected, 631mg (73%). HRMS calcd. for C₁₁H₈N₂O₅, 249.0511 found 249.0517.N-(2-Hydroxyphenyl)-5-nitrofuran-2-carboxamide (10a, 151 mg, 0.6 mmol)was dissolved in 6 mL of toluene containing p-toluenesulfonic acid,monohydrate (700 mg, 3.7 mmol) and the reaction was heated to refluxovernight. The reaction was concentrated in vacuo then purified througha silica gel column eluting with dichloromethane and increasing polarityto 10% EtOAc:dichloromethane to collect product 11a as a yellow-greensolid, 62 mg (44%). ¹H NMR (300 MHz, CDCl₃) δ 7.87-7.81 (1 H, m),7.67-7.62 (1 H, m), 7.46 (4 H, m); HRMS calcd. for C₁₁H₆N₂O₄, 231.0406found 231.0423. LC/MS Retention time 7.53 min (<95%), FABMS 231.3 (M+1).

2-Nitrothiophene-4-carboxylic acid (7b, 200 mg, 1.1 mmol) was dissolvedin 5 mL of dry acetonitrile and then the EDCI (434 mg, 2.2 mmol), DMAP(414 mg, 3.4 mmol) and 2-aminophenol (9, 137 mg, 1.2 mmol) was added.The reaction was stirred at room temperature overnight under argon. Thereaction was concentrated in vacuo to dryness then diluted with EtOAc(75 mL) and then the organic phase was washed 2× with 0.5 N citric acid,2× with aqueous 10% sodium bicarbonate and satd. brine solution. Theorganic phase was dried over sodium sulfate and concentrated to give ared solid. The residue was triturated with dichloromethane to giveproduct 10b which was collected by filtration, 219 mg (73%). The crudeN-(2-hydroxyphenyl)-5-nitrothiophene-2-carboxamide (10b, 219 mg, 0.83mmol) was dissolved in 6 mL of toluene containing p-toluenesulfonicacid, monohydrate (788 mg, 4.14 mmol) and the reaction was heated toreflux overnight. The reaction was concentrated in vacuo then purifiedthrough a silica gel column eluting with a gradient from puredichloromethane to 5% EtOAc:dichloromethane to give product 11b as anoff white solid, 99 mg (49%) after evaporation of the solvent. ¹H NMR(300 MHz, CDCl₃) δ 8.58-8.55 (1 H, m), 8.31 (1 H, d, J=1.78 Hz),7.80-7.75 (1 H, m), 7.63-7.56 (1 H, m), 7.45-7.36 (2 H, m); ¹³C NMR (126MHz, CDCl₃) δ 157.26, 150.41, 141.47, 132.12, 127.02, 125.97, 125.15,120.37, 110.75; HRMS calcd. for C₁₁H₆N₂O₃S, 247.0177, found 247.0177.LC/MS Retention time 8.35 min (<95%), FABMS 247.3 (M+1).

Although certain embodiments have been illustrated and described herein,it will be appreciated by those of ordinary skill in the art that a widevariety of alternate and/or equivalent embodiments or implementationscalculated to achieve the same purposes may be substituted for theembodiments shown and described without departing from the scope. Thosewith skill in the art will readily appreciate that embodiments may beimplemented in a very wide variety of ways. This application is intendedto cover any adaptations or variations of the embodiments discussedherein. Therefore, it is manifestly intended that embodiments be limitedonly by the claims and the equivalents thereof.

What is claimed is:
 1. A method of treating a drug-resistant bacterialstrain, comprising: administering a compound to an individual infectedwith or suspected of being infected with a methicillin-resistantStaphylococcus aureus strain, a vancomycin-resistant Enterococcusstrain, or a linezolid-resistant Enterococcus strain, wherein thebacterial strain is killed or inhibited from growing, wherein thecompound is one of the following compounds:


2. The method of claim 1, wherein the compound is:


3. The method of claim 1, wherein the compound is:


4. The method of claim 1, wherein the compound is: